net: tcp2: Don't instantiate an extra connection on SYN+ACK
net: tcp2: Don't instantiate an extra connection on SYN+ACK

On incoming SYN+ACK, use the existing TCP connection.

This problem was overlooked earlier and was found while
testing TCP2 client side.

Signed-off-by: Oleg Zhurakivskyy <cdb82bfa180f8df716a77d2c2557196a597a233c@intel.com>

finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr